Generally, meteorological radars measure precipitation by transmitting radio waves over 360° around the radar concerned and receiving reflection wave (echo) signals caused by the transmitted radio waves reflecting on cloud or rain. The reflection wave signals contain not only echo components of cloud or rain that are observation targets, but also static clutter components that are unnecessary reflection wave components caused by the transmitted radio waves reflecting on static object(s) that is not the observation target. The static clutter components mainly contain ground clutter components that are reflection wave signal components of land.
Such static clutter components cause degradation in accuracy of rain amount calculation in meteorological observation. Therefore, conventional meteorological radars are provided with signal processing devices that perform Moving Target Indicator (MTI) processing so as to suppress such static clutter components (e.g., see JP2011-169829A).
The meteorological radar signal processing apparatus described in JP2011-169829A includes: an MTI processor that computes ground clutter components from the reception signals of a target-reflected wave, on the basis of the predetermined MTI parameters and removes them; a speed width filter that compares signals in which the ground clutter component is removed by the MTI processing with a threshold based on a predetermined speed width parameter, and extracts meteorological echo components included in the signals processed by the MTI processing; and a meteorological information computing section that obtains meteorological information from the output of the speed width filter.
By this configuration, with the apparatus described in JP2011-169829A, observation data and simulated weather echo at the radar installation point obtained in fine weather are used to automatically search optimal values of the MTI parameter and the speed width parameter, and the automatically searched MTI parameter and speed width parameter are set in the MTI processor and the speed width filter in advance, so that parameters can be automatically adjusted by simulation in an off-line mode.
However, with the apparatus described in JP2011-169829A, since the observation data in fine weather is used, it is difficult to improve the accuracy of rain amount calculation in meteorological observation.
Such a difficulty is caused due to echo components of a static object such as land or a building (especially echo components of land) significantly increasing in level and variation in fine weather compared to when raining, which leads to obtaining unstable observation data in fine weather.
Thus, if the observation data in fine weather is used, the echo components of the static object are not suppressed enough and remain, or the echo components of the static object are overly suppressed which causes over-suppression of echo components of rain (rain components). As a result, with the apparatus described in JP2011-169829A, it is difficult to improve the accuracy of rain amount calculation in meteorological observation.